OEtrSTACEA. 255 



exists on tlie fifth siegment ; the terminal segment is much narrower 

 than the preceding, acute and constricted at base. The eyes are 

 placed in very small orbits ; the antennules lie in oblique fossettes ; 

 the bases of the antennse are almost completely fused with the sur- 

 rounding parts of the carapace (in the single specimen examined), 

 and scarcely any trace remains of a flagellum. The merus-joint of 

 the outer maxillipedes is triangulate, and shorter than the preceding ; 

 the exognath has its outer margin straight, and, although robust, is 

 narrower than the ischium of the endognath, it does not reach to 

 the extremity of the merus-joint. The cheUpedes are subequal and 

 of moderate length, with the joints granulated, but otherwise un- 

 armed ; merus trigonous ; carpus very short ; palm externally rather 

 convex, with an angulated prominence on its inner surface, shorter 

 than the fingers, which externally are longitudinally sulcated, meet 

 along their inner margins when closed (these margins being minutely 

 denticulated), and are concave internally toward and somewhat 

 incurved at the tips. The ambulatory legs (which are partially 

 concealed beneath the carapace) have all the joints strongly gra- 

 nulated ; the dactyle slender, and longer than the preceding joints. 

 The colour (in spirit) of the single specimen is nearly white. Lefigth 

 not quite 3 lines (6 miUim.), breadth nearly 4 lines (8 miUim.). 



The single specimen was collected at Port Molle, 5-12 fms. 

 (No. 118), and is a male, the first, I believe, recorded of this genus. 

 The very prominent front seems to distinguish this species from 

 aU hitherto recorded, except Oreophorus petroeus*, from New 

 Caledonia, which is only distinguished by the much shorter, 

 more dilated immobile fingers of the chelipedes, and by having the 

 lateral margins of the carapace marked by three closed fissures, 

 whereas in 0. frontalis there are but two, which meet behind and 

 circumscribe the hepatic region. There are two specimens that 

 probably belong to 0. petrceus in the collection of the Museum, from 

 Shark Bay, W. 'Australia (F. M. Bayner, H.M.S. ' Herald '). These 

 forms are certainly intermediate between Oreophorus and Ths, but 

 seem to me to have more afSnity with the former genus, since in 

 Tlos muriger. Ad. & White (the typical species), the front is not at 

 aU prominent, and its margin, with the antero-lateral margins of 

 the carapace, is dorsaUy reflexed. 



In the elongated fingers it resembles 0. rugosus, Stimpson, as 

 figured by A. MiLne-Edwards t, from the Loochoo Islands and Cochin 

 China, which, however, has a much less prominent front and the 

 carapace more coarsely punctulated, and is without the hepatic 

 sulcus. Mr. Haswell (Cat. p. 130) records 0. rvgosus from Port 

 Denison ; but as his description is merely abbreviated from that of 

 Milne-Edwards, I am unable to say whether the specimens there 

 collected afford any basis for uniting 0. rugosus and 0. frontalis. 



* Tlos petrieus, A. M.-Edwards, Nouv. Arch. Mus. Hist. Nat. x. p. 51, pi. iii. 

 t Ann. Soo. Entom. France, sfir. 4, t. p. 152, pi. yi. fig. 3 (1865). 



